Ryan, the T foils for a cat that you want to use as a “pitch” control I.E to stop (or dampen) the bows from diving AND rising dramatically, needs to be of a symmetrical profile (Luis’s post goes into a range of effects of different profile foils which could confuse the issue if you all you want from them is for the cat to be more stable fore and aft). Personally I feel that cats that could benefit the greatest of any of those cats “out there” at present are the Hobie 14 and 16.
As a pitch control, you want to ascertain the “ideal attitude” that you would want the hulls to be sailing at if you were sailing on the proverbial dead flat, smooth surface, and the wind was absolutely constant. (No such conditions could ever exist but we can dream), then project a line parallel to the “flat surface” from bow to stern of the hulls. Transpose that line onto the rudders in their fully down, “locked” position. That line then becomes the centreline of the foils, as that is the angle to the water surface that ideally you want the hulls to be sailing at all of the time, regardless of any “outside forces”.
You want symmetrical foils because you want lift to be generated both up or down depending on which way that the hulls are “tending” to pitch, so that the lift acts as a self regulating equal and opposite countering force to that “pitch”
As the bows of a Hobie 14 in particular, are so low in buoyancy, I personally think that I would set the T foils for them with a couple of degrees of positive lift rather than neutral I.E. set them up as described above then before fixing them into their final position angle them front down just a touch (2 or 3 degrees which is very small)